Catalytic hydrogenation of acetophenone to phenyl methyl carbinol



Patented Nov. 20, 1951 CATALYTIC HYDROGENATION OF ACETO- PHEN ONE TO PHENYL METHYL CARBINOL Howard B. Guest and Raymond W. McNamee, South Charleston, W. Va., assignors, by mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York No Drawing.

Original application August 7,

1944, Serial No. 548,510. Divided and this application April 26, 1949, Serial No. 89,794

6 Claims.

This invention is an improvement in processes for making phenyl methyl carbinol by hydrogenation of acetophenone. More particularly the invention provides a rapid catalytic process for hydrogenating acetophenone selectively to phenyl methyl carbinol with good yields and efficiencies. It includes, also, an improved ironcopper-chromium catalyst and a method of preparing the catalyst.

It is known that acetophenone may be hydrogenated to form phenyl methyl carbinol. Phenyl methyl carbinol is important as an intermediate in the production of styrene. According to one series of reactions, ethyl benzene may be oxidized to acetophenone, acetophenone hydrogenated to phenyl methyl carbinol, and the carbinol dehydrated to styrene. It is to be noted that in this series of reactions none of the reagents used or by-products formed in the main reactions are of the nature of difficultly removable impurities which may remain to adversely affect, even in traces, the quality of the ultimate product, styrene. The only by-product is water which is readily separated and, aside from the base material undergoing conversion to styrene or an intermediate, the only reagents are the readily available, low-cost materials, oxygen and hydrogen.

Although, in the reduction of acetophenone by hydrogen, the only product of the main reaction is phenyl methyl carbinol, not all catalysts are sufficiently selective in their action to form the main product to the exclusion of side reaction products. In some instances, the formation of products by side reaction may increase disproportionately with increase in catalytic activity or other conditions resulting in an increased rate of the main reaction.

Among possible side reaction products are ethyl benzene and cyclohexyl methyl carbinol. In the dehydration of phenyl methyl carbinol to styrene, any cyclohexylmethyl carbinol present therein would be simultaneously converted to vinyl cyclohexane while any ethyl benzene present would pass through unchanged. The boiling points of both vinyl cyclohexane and ethyl benzene lie so close to that of styrene that their separation from styrene by distillation is not easily accomplished. Although no difficulty is encountered in separating ethyl benzene from phenyl methyl carbinol in view of the wide difference in their boiling points, a somewhat different situation is presented by the high boiling cyclohexyl methyl carbinol which distills only about 14 C. below phenyl methyl carbinol at normal pressure, with even less difierenee at reduced pressures.

We have discovered that phenyl methyl carpredominating amounts, computed on a metal basis.

The catalyst may conveniently be prepared by I roasting a mixture of the hydroxides and carbonates of the metals to convert them to the oxides, and for this purpose roasting temperatures from 200 to 450 C. and roasting periods of from one to twelve hours, depending upon the temperature, may be used successfully. Usually, however, catalysts of good activity may be obtained by roasting the mixture at a temperature from about 250 to 350 C. for a period which need not exceed six hours. At temperatures of about 275 to 315 C. which are preferred, catalysts roasted for about three hours are more active than those roasted for a longer period. The decomposition of the carbonates to the oxides proceeds smoothly in contrast to the strongly exothemic decomposition accompanyin the preparation of some catalysts heretofore proposed, and it may be carried out readily on a commercial scale.

In preparing the catalyst, a. mixture of iron, chromium and copper hydroxides, carbonates, and basic carbonates suitable for roasting may be obtained by precipitation from an aqueous solution of the metals in the form of such soluble salts as the nitrates, acetates or the. like. The precipitating agent may be an aqueous solution of sodium carbonate, ammonium carbonate or other soluble carbonate. This procedure has the advantage that the remaining salts formed by the metathesis are water-soluble and easily washed from the precipitate. Before convert ing the mixture to the oxides, it may be found desirable to wash the precipitate to remove water-soluble salts and subject the washed precipitate to a preliminary drying at a temperature of about 0 to C. over a period of 10 to 20 hours approximately.

During the roasting procedure a very small amount of water-soluble chromates may be formed. It may be found advantageous to remove these before using the catalyst. This can be done by washing the powder on a filter or by lixiviation with hot water until the wash water shows a negative test for the chromate ion. The ordinary test is made with silver nitrate solution, a red precipitate indicating the presence of chromate.

.The copper used in making the solutions is.

preferably of electrolytic grade and the iron of a purity equivalent to Armco Ingot. Similarly,

3 the chromium salts should be of equivalent p y In carrying out a hydrogenation of acetophenone using the mixture of oxides as first ob: tained by decomposition of thehydroxidesand, carbonates, an induction periodmay beobse'ryed. During this induction period, the catalyst" apparently undergoes a reduction with formation of; water. Where it is desired to avoid the formation. of water in hydrogenating the acetophenone, or where the hydrogenation is to be carried out in a continuous-type process, it maybe advanta: geous first to heat the catalystin the presence or hydrogen to activate it. For instance, after the precipitate has been converted to the oxides, a stream of hydrogen may,be passed through the roasting kihi while theroasted material is maintained-"at an elevated temperature-forseveral hours; The efflue gases maybe passed through a'cohdenserto'liquefy the water vapor and when no more water is condensed, the activation may be considered to be completed.' Another method of activating the mixed oxides includes suspending the roasted material in ethyl benzene and then heating the mixture "with hydrogen under pressure. The water which is formed may be vented from the autoclave from time to-time. In activating the catalyst by 'heatingit'in thepresence of hydrogen, a temperature of 150-to 200 C.- is preferred, but higher and lower temperatures may also be used.

Prior to activation the catalyst is not magnetic butiitbecomesmagnetic upon activation. The diffraction patterns obtained with cobalt radiationin X -ray studies of the catalyst revealed lines corresponding to the patterns for magnetic oxide of iron (FeaOr), copper, and cuprous oxide, C1120. The'g'rain sizes of all the constituents were very l p "After activation, the solid catalyst may be stored by covering it with acetophenone or ethyl benzene, for instance, to protect-it. Slurries containing as much as 20 percent by weight of solids may be handled and transferredconveniently.

For producing phenyl methyl carbinol selectivelyby hydrogenation of acetophenone, the most useful catalysts are those inwhich the copperand" chromium are present, on a metal basis, in a proportion from about 71' to 109 parts of copper and about 8 to 17 parts of chromium per 100 parts of 'iron.' Using such. a catalyst, v the hydrogenation not only proceeds at a high rate with negligible amounts of ring hydrogenation and ethyl benzene formation, but the reaction may'alsdbe carried'out attemperatures and pressures which are low in comparison with those which are employed in hydrogenation processes generally; andphenyl methyl carbinol is obtained ingood yield. The catalyst is characterized also by its good stability and resistance to catalyst poisons. It has the additional advantage that it may be prepared with relative ease from raw materials of relatively lowcost- I Catalysts containing about 95 to 96 parts of copper and from about 8 to l7parts of chromium per 100 parts of iron are superior in activity to those having a higher or lower proportion of chromium. similarly, catalysts containing about 10.5 to 14.5 parts of chromium to /1 of the total amount of copper and iron) and from about 71 to 109 parts of copper per l00'parts of iron are superior to those having a higher or lower proportion of copper to iron; Our best results were obtained with catalysts in which copper and chromium were present in a ratio of about 95 to 96 partsof copper,.(46 per: cent) and about 12 to 13 parts of chromium (fibercent); per 100 parts of iron (48 per cent), on a metal basis.

To assist in the removal of the catalyst from the hydrogenation product, other materials such as diatomaceous earth, kaolin, fullers earth and the like may be incorporated in the catalyst, for instance, by adding them to the salt solution prior to precipitation of the mixture of the carbonates of the metals. Such materials may also serve to extend the catalyst" and enhance the activity of the active constituents.

The hydrogenation may be carried out at an elevated temperature and under hydrogen pressure in a conventional pressure reactor. In general, from about 0.5 to 10 parts of catalyst per 100 parts of acetophenone are suitable in carrying out thereaction, but-an excess of catalyst-is not of itself objectionable. Depending largely upon the catalyst concentration, the hydrogena tion may be carried out using hydrogenpressures;

as low as 50 to 100p. s. i.- and-at temperatures ranging from 130 to 175C. p. s. i. as used hereinis meant pounds per square inch, gage.)- Higher pressures and temperatures may be used if desired, but ordinarily it is unnecessary to resort to pressures much above 150 to 200 p. s. i. or to temperatures substantially higher than 200 C.- Qn the other hand,-

at temperatures of about to- -C.- or below,

the rate of hydrogenation may becometoo slow to be practicable, except possibly at high hydrogen pressure or high catalystconcentration. The hydrogenation maybe carried out in-a continuous manner by spraying a mixture of acetophenone and catalyst into an atmosphere of hydrogen under suitable pressure.

they are more rugged and durable than catalysts which do not contain iron in the specified ratio; This is especially true at/higher reaction temperatures and becomes evident ina striking way when the catalysts are used in a continuous process Where high activity over'a protracted period is essentialto successful commercial operation.

The invention may be further-illustrated bythe following examples:

EXAMPLE 1 A. precipitateof the mixed carbonates-of. iron,

copper and chromium was madeby adding a.- saturated, aqueous solution of sodium carbonate. to an aqueous solutioncontaining 262 grams of: chemically pure ferric nitrate. nonahydrate, Fe(NO3)3.9l-I2O; 26.5, grams of chromic nitrate.

nonahydrate, Cr(NO3)3.9HzO;. and:121.'7 grams.

of cupric nitrate trihydrate, Cu(NOa)z.3HzO, dis-. solved in 1.5 liters of distilled water. Duringthe. precipitation, the solution'was maintained at a temperature of 50 C. and vigorously.agitated. After filtering, the precipitatewas lixiviatedwith three successive portions of water of 1.5 liters each, and air dried in an oven at 120 0., followed by roasting at a temperature of 290 C: for a period of 1.5 hours. The roasted material;

was then leached withboiling water in three suc- 76 cessive portions of 0.4 liter each and activated (By the symbol- Thecatalyst-may berecovered by filtering, settling and the like, after by reducing it in an atmosphere of hydrogen for a period of three hours at a temperature of about 175 C. After purging the hydrogen from the reducing chamber with nitrogen, the activated continuously until the mixture reacted basic to phenolphthalein. The total amount of sodium carbonate solution was 130 parts, and about one hourwas required for the addition. After the material was transferred to a container filled with 5 stirring had been continued for about one-half acetophenone and stored until used. hour with the temperature maintained at 90 to There were obtained 90 grams of activated 100 C., the resulting precipitate of carbonates catalyst which was found, by analysis, to contain and basic carbonates was permitted to settle for 9.45 parts of chromium and 88.4 parts of copper. several hours. About one third of the superper 100 parts of iron, by weight. natant liquid could be decanted as clear liquor, EXAMPLE 2 and; the remainder was removed by filtration. r The solids obtained by filtration were charged Following the procedure of Example 1, a catainto a rotating drum of suitable size, a small lyst was made using 54.2 grams of ferrous sulfate stream of air was then passed through the drum heptahydrate; FeSO4.7H2O; 11.5 grams of chro-' 5' and the temperature brought as quickly as posmic nitrate nonahydrate, and 39.3 grams of sible to 300 C. The roasting of the precipitates cupric nitrate trihydrate. was continued for two hours at a temperature The activated catalyst which was obtained -"maintained at 300 to 325 C. The catalyst thus analyzed 13.1 parts of chromium and 94.5 parts obtained was then leached five times with succesof copper per 100 parts of iron. sive portions of water of about 60 to 65 parts each, and the leached catalyst charged to the EXAMPLE 3 roasting drum where it was dried in a current of Aca alyst Wa ma e according to the proce u air for about one-half hour at a temperature of of Example 1, Sta g W l iron (AImCO 120 C. The catalyst was then passed through me p c pp e tro yt c bus bar scrap) a mesh sieve. A mixture of ethyl benzene and commercial chrom1um acetate solution (12 d th powdered catalyst (10 per cent catalyst) P cent Q was then charged into an autoclave where it was The activated catalyst was found, by analysis, heated t about 75 Q in the presence of to contain 9.45 parts of chromium and 88.4 parts droge mamtanied at a pressure of 75 of copper per 100 parts of iron. 30 Water formed in the activation of the catalyst EXAMPLE 4 was removed by venting the autoclave to about t 25 pl's'. i. at intervals of 30 minutes. At the end From grams of m f ednonahy of three hours no more hydrogen was absorbed, $5 332 9 f i a ate indicating that the activation had been com- 1 grams a g"? e y i $25: pleted. The activated catalyst thus obtained ys Y 22??? f 3 9 was used in the hydrogenation of acetophenone. g i g 2 d i t g i u 55 ig The catalyst had good activity and converted W p 8V y W m acetophenone selectively to phenyl methyl caracld were t q m the l Solution prior binol to the exclusion of side-reaction products. to the prec1p1tat1on of the mixed carbonates of Acetophenone was hydrogenated to phenyl the metals 40 methl carbinol using catalysts prepared in ac- The resulting catalyst was found to contain y cordance with the foregoing examples. In each 95.2 parts of copper and 13.1 parts of chromium per 100 parts of iron of the runs the charge comprised 200 parts, by

weight, of an acetophenone-phenyl methyl car- EXAMPLE 5 binol mixture containing from about-80 to 90 per Into a stainless steel drum were charged 17.7 cent agetophenope to which was added from parts of a solution containing 13.6 per cent iron 9 10 parts. by g ht, of catalyst. The charge in the form of ferric nitrate; 17.55 parts of a was placed in a suitable autoclave and mamolution containing per cent copper in the tallied. at a temperature of about 145 to 150 C. form of cupric nitrate; 3.75 parts of chromium ll? hydrogen Introduced under a pressure acetate solution containing the equivalent of 12 Of 1219011131 50 D- S- At t p o of t e percent of chomium trioxide (ClzOs) and runs the Ca y W p ed to settle and w s parts of wamr. The temperature. of the charge filtered from p du and h p ent of was maintained at to C. and a ten per acetophenone and ethyl benzene determined. cent solution of aqueous sodium carbonate added 55 Data for a number of runs is given in Table A.

' TableA 0 t1 t0 Charge 3 i 9 Product 1223. 38:

{Igmp., Pressure, Time, genation, Aceto C. p. s. 1. Hours Acet0 Ethyl P3121122: of itittli Catalyst time 55917 w 80.3 1 95.8 12.5 145 145 7.0 25.7 0.1 7.7 80.3 1 95. 8 12. 5 175 s. 5 18.5 0. 8 19. 7 80.3 4 95.8 12. 5 145 1. 8 19. 5 0. 2 33.8 80.3 4 95. 8 12. 5 140 1. 8 5. 4 4. 5 41. 5 80. 5 4 95. s 12. 5 178 135 0. 9 22. 4 4. 7 54. 4 80.3 20 95.8 12.5 143 155 0.9 18.4 0.9 68.8 80.3 20 95. 8 12. 5 120 140 2.1 13.8 0. 2 31. 7 50.3 4 95.8 12.5 100 950 1.8 12.9 0.2 37.5 84.0 5 95.8 12.5 147 5.0 22.4 17.1 84.0 5 95.8 12.5 147 150 4.0 7.3 19.2 84.0 5 95.8 12.5 148 r 150 5.0 12.2- 14.8

1 Parts per 200 parts of charge. 2 Parts per 100 parts of iron. 1

3 Included also 208.3 parts of diatomaceous earth, V 4 Included also 208.3 parts of fuller's'eartli.

l Included also 208.3 parts of kaolin.

gamma A; number ot'nms -lwere :alsoi'mader 1m which! a: catalyst waszusedioverrandioveruagaim Inieaclr oifthe1 runs'230 partszof a supportedfcatalystiwere" used 'pen200 parts :of a chargeiwlileliiwasra mix ture of acetophenonetand plienylJmetliyl-carbinoii The catalyst had the following-composition on'ia' metal 1 basis by weight: iron; 10!! parts; copper; 94L9 parts chromium; 13:3 parts; and' silica wFil trostsilica type), 1843 parts Data for these runs illustrating"theadurabilityof the iron-copper chromium mlxeddoxide cam lyst are givenin Table-BI 95* 11019.6 parts of icopper: and abolitE-B to 17 p'arts of: chromium per 1001"parts:-oi iron; saidilcatalysu upon activation, being characterized by being magnetic: and by: exhibiting": lines: corresponding CllzO; and copperlinidifiraction patternsiobtained by cobaltradiationi ii-A method; for' producing: phenyl methyl: carbin'ol'z by reduction of acetophenone which comprises introducing hydrogen into acetophenone under pressure" and at a temperature of about 125 to 200 C. in the presence of an iron Table B.

3 Product Rate oi'n' Aceto- Hydrophenonei Tampa Pressure," Time genation, in charge O.- p. s.-i.-- Hours Aoeto-I' Ethyl per-cantor per cent phenolic, Benzene, charge per Percent Percent hour 94. 5 150 150 4: D 9.3 21. 2 150 150 4:-@ 3. 2 23. 8 9(5 I 150 150 31) 2:5 30. 7 7910 150 150 335 6L0 20E 9* 79.0 150 150- 3:0; 5. 7 2454-" 79.0 146 150 4. 5 154 8: 14. 1, 791)" 152 150' 4:5 3.8 16.7 7941i- 152 150- 3. 5 g 32.7 13.2 79. 152 150 K0 1238 13. 2 79L 0 152. 150 4; 51. 13. 7 14. 5 79.1) 150: 150 5. 5 A- 12. 5 79:0 155 150" 4. 0 l4. 0 16.2.1

This application is a. division of our copending application filed'August 731944, Serial No. 548,5l0 nowEatent No. $544,756.

We claim:

1." A method for producing, phenyl" methyl carbinol by, reduction of"acetophenone whicl r comprises introducing hydrogen intol'acetoph'eenone under a pressure of at le'astSO p! siiina'nd'at a temperature ofat least125T'C. inthepresence of 'a catalytic amount of an iron-copperechromium. mixedfoxides hydrogenation catalystjiin which copper and chromium are presentin a ratio computed on a" metal basis, by weight; of aboutll to 109 parts of "copper andabout8 toil-7 parts .of chromium per IUOLparts' ofv iron, saidl'cat' alyst, upon activation, being, characteriz'edbyi-being magnetic and. byv exhibitingjines correspond; ing to magnetic oxide of iron, FesOi; cuprous oxide, vcuzo; and copper in diffraction patterns obtained bycobalt'radiationx 2;" A method for producing phenyl; methyl carbinol by reduction of acetophenone which" comprises introducing hydrogen intoiacetophenone underv a pressure of at least p, s2 Land'at" a temperature of 'at'least 125 'C'LTin'the presence: of a catalytic amount ofan iron'-copper chi'o= mium mixed oxides hydrogenatiom cataliyst in which copper and chromium are presentina-ratio computed on a metal basis, by weight, of about 71 120.109 parts of copper and about 10.5.to 14.5 parts of chromium per 100" parts :oi'= Tiron;.asald" catalyst, upon activation,: being characterized by: being magnetic and by exhibiting lines corre-- sponding to magnetic oxide of iron; Fea0acuprous oxide; C1120; and copper:in"difiraction patterns obtained by cobalt radiation.

3; A method for producing phenyl methyl oarbinol by reduction of acetophenone which comprises introducing hydrogen into acetophe-r none under a pressureof at least sop; s. i. and at I a temperatureof at least125i C. 'in:the presence of a catalytic amount of an iron-copper-chro-i mium mixed oxides hydrogenation catalystin which copper and chromium are present in a ratio computed on a metal basis, by weight, of abtmtli7t? copper-chromium mixed oxides hydrogenation catalyst in which copper and chromium are presentlinwa ratio computed onrametal basis-by weight, of about 1 1 to". 109' parts" of 1 copper and about 8 torl'? parts of chromium per parts of iron, said catalyst, upon activation, being characterized" by being:v magnetic and by."- exhibiting lines: corresponding; to magnetic oxide/ 0f iron, Feaoipcuprous'oxide;'Cu2O; and copper in diffraction patterns obtainedv by. cobalt radiation:

5. A method for producing phenyl; methyl carbinol by; reduction of acetophenone: which comprises;- introducing thydrogen' into acetophe= home under a pressure of about 5'0L=to. 200ip. s-.:i; and at a temperature of about to 200 C. in the presence of an iion-copper-chromium mixed oxides '-h ydrogenatio n catalyst 1 in which" copper and chrom'iumare present in a'ratio' computed on a metal basis, by weight,-of about 7 1 to 109-parts of copperand about 8 to 17 'parts'ofbhromium per lon parts of iron, saidcatalyst; upon activaum;- beingcharacterized by being magnetic and by exhibiting lines corresponding to magnetic oxide of" iron; moi; cuprous 'oxide; C 120; and copper ir'r diiiractionpatterns obtained by'cobalt' radiation;- I

6. A method for producing phenyl methyl carbinol by reduction of acetophenone which comprisesiintroducing hydrogen into acetophenone under a pressure of about 50 to 200 p. s. i. andatatemperature-ofabout to C. in the presence of an iron'-copper-chromium mixed oxides hydrogenation catalyst in which copper andichromium are present in a ratio computed .-;on& a metal basis, by weight, of about '71 to 109 parts-of copper and about 8 to 1'7 parts of chromiumper:l00 parts-of iron, said catalyst, upon activation, being characterized by being magnetic and by; exhibiting lines corresponding to magnetic oxide of iron, F6304; cuprous oxide, CuzO; and copper in difiraction patterns obtained by cobaltradiation.

HOWARD R. GUEST. RAYMOND W. MoNAMEE.

(Rcferences'on .following page) REFERENCES CITED Number The following references are of record in the $110,433 file of this patent: UNITED STATES PATENTS 5 Number Name Date 2,040,913 Amend May 19, 1936 Number 2,047,945 Arnold et a1 July 21, 1936 5871181 10 Name Date Guyer Mar. 8, 1938 Soday Aug. 25, 1942 Hughes July 6, 1943 FOREIGN PATENTS Country Date Great Britain Apr. 16, 1947 

1. A METHOD FOR PRODUCING PHENYL METHYL CARBINOL BY REDUCTION OF ACETOPHENONE WHICH COMPRISES INTRODUCING HYDROGEN INTO ACETOPHENONE UNDER A PRESSURE OF AT LEAST 50 P.SI.I. AND AT A TEMPERATURE OF AT LEAST 125* C. IN THE PRESENCE OF A CATALYST AMOUNT OF AN IRON-COPPER-CHROMIUM MIXED OXIDES HYDROGENATION CATALYST IN WHICH COPPER AND CHROMIUM ARE PRESENT IN A RATIO COMPUTED ON A METAL BASIS, BY WEIGHT OF ABOUT 71 TO 109 PARTS OF COPPER AND ABOUT 8 TO 17 PARTS OF CHROMIUM PER 100 PARTS OF IRON, SAID CATALYST, UPON ACTIVATION, BEING CHARACTERIZED BY BEING MAGNETIC AND BY EXHIBITING LINES CORRESPONDING TO MAGNETIC OXIDE OF IRON, FE304; CUPROUS OXIDE, CU20; AND COPPER IN DIFFRACTION PATTERNS OBTAINED BY COBALT RADIATION. 